Engineering Notes by Oriental Motor

Minimizing the Effect of Load Fluctuations for Mixers

[fa icon="calendar"] Jun 30, 2020 12:00:00 PM / by Johann Tang

Johann Tang

The viscosity change in liquids can vary the torque required for mixing.  For AC asynchronous motors such as AC induction motors, the rated speed is affected by load torque fluctuations, which may cause inconsistency in the final product.  Is there a better motor for the job?

Challenge Mixing liquids of different viscosity at stable speeds


Mixer with AC motor


Conventional Equipment

We show a traditional hand-held mixer here. 

Typically, a 3-phase AC induction motor is selected as the motion device for a mixer.  A variable frequency drive (VFD), or inverter, is used to control the speed of the motor.

Problems with Conventional Equipment

The viscosity can change during mixing.  This causes the load torque to fluctuate, which changes the speed of the motor, resulting in inconsistent quality.


How viscosity can affect load torque


Solution Use a brushless motor with closed-loop feedback

Brushless motors operate with closed-loop feedback from hall-effect sensors.  This ensures tight speed regulation even with load fluctuations.  Compared to AC motors, brushless motors are also much more efficient and therefore more compact.  The constant torque output from brushless motors also ensures the same torque being applied (up to rated speed).  Brushless motors also offer a wider speed range when compared to AC motors driven with VFDs.  


Mixer with brushless motor


Brushless Motor Benefits

  • Smaller
  • Lighter
  • Higher efficiency
  • No fan necessary
  • Lower operating temperature
  • Constant torque output
  • Wider speed range
  • IP65/IP66/IP67 protection

Smaller and Lighter Design

Upgrade an AC motor to a brushless motor for smaller and lighter designs.  More details can be found in the comparison table below.

Comparison Between AC Induction Motors and Brushless Motors (Round-Shaft Type)

Comparison between AC induction motors and brushless motors


BMU Series

BLH Series

External View

BMU Series motor and panel mount driver BLH Series BLDC motor and compact driver

Power Supply Input

Single-Phase 100-120 VAC
Single/Three-Phase 200-240 VAC
24 VDC


30 W, 60 W, 120 W, 200 W, 400 W 15 W, 30 W, 50 W, 100 W

Speed Regulation (Load)

±0.2% (Digital) ±0.5% (Analog), ±0.2% (Digital)

Speed Control Range

80~4000 RPM 80~3000 RPM

Speed Setting Method

Digital Digital/Analog/RS-485


TIP: for low speed applications
Brushless motors cover a wider speed range than AC motors driven by VFDs.  This means that brushless motors can operate at a lower RPM and higher RPM.  For example, the BX II Series can operate as low as 0.01 RPM (with a 200:1 gear ratio).  The reason is because the BXII Series brushless motors use encoders instead of hall-effect sensors.

Brushless gear motor with H1 food grade grease

For mixers or agitators that are used for food applications, brushless gear motors with H1 food-grade grease are available. 

Gear motors with H1 food-grade grease are currently available from BMU Series and BLE2 Series.  Please contact our technical support team for more information.


Contact Our Experts

H1 food-grade grease info


Thanks for reading this post.  Here are some videos for the products discussed in this post.

Here's a video introducing brushless motors as the new standard in speed control.

Here's a video of a BMU Series brushless motor with its speed controller (driver) on a belt conveyor.

Here's a video of BLH Series brushless motors demonstrating driving and steering in an AGV.


Browse All Brushless Motors

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Topics: Speed Control, VIDEOS, BLDC Motors, Gearheads, Washdown, Application Examples

Johann Tang

Written by Johann Tang

Johann Tang is a Product Specialist at Oriental Motor USA Corp. with 20+ years of experience in sales, technical application support, and training of various types of fractional horsepower electric motors, gear motors, actuators, drivers, and controllers. Feel free to ask him questions on Linkedin.

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